1. CELL DIVISION AND REPRODUCTION © 2012 Pearson Education, Inc.

2. Cell division plays many important roles in the lives of organisms  Organisms reproduce their own kind, a key characteristic of life.  Cell division –is reproduction at the cellular level, –requires the duplication of chromosomes, and –sorts new sets of chromosomes into the resulting pair of daughter cells. © 2012 Pearson Education, Inc.

3.  Cell division is used –for reproduction of single-celled organisms, –growth of multicellular organisms from a fertilized egg into an adult, –repair and replacement of cells, and –sperm and egg production. Cell division plays many important roles in the lives of organisms © 2012 Pearson Education, Inc.

4. Cell division plays many important roles in the lives of organisms  Living organisms reproduce by two methods. –Asexual reproduction –produces offspring that are identical to the original cell or organism and –involves inheritance of all genes from one parent. –Sexual reproduction –produces offspring that are similar to the parents, but show variations in traits and –involves inheritance of unique sets of genes from two parents. © 2012 Pearson Education, Inc.

5. Figure 8.1A Asexual Reproduction

6. Figure 8.1D Sexual reproduction produces offsprings with unique combination of genes

7. Figure 8.1E Dividing cells in an human embryo A human kidney cell dividing

8.  Prokaryotes (bacteria) reproduce by binary fission (“dividing in half”).  The chromosome of a prokaryote is –a singular circular DNA molecule associated with proteins and –much smaller than those of eukaryotes. Prokaryotes reproduce by binary fission © 2012 Pearson Education, Inc.

9.  Binary fission of a prokaryote occurs in three stages: 1.duplication of the chromosome and separation of the copies, 2.continued elongation of the cell and movement of the copies, and 3.division into two daughter cells. Prokaryotes reproduce by binary fission © 2012 Pearson Education, Inc.

10. Figure 8.2A_s3 Plasma membrane Cell wall Duplication of the chromosome and separation of the copies Continued elongation of the cell and movement of the copies Prokaryotic chromosome 1 2 3 Division into two daughter cells

11. Figure 8.2B Prokaryotic chromosomes

12. THE EUKARYOTIC CELL CYCLE AND MITOSIS © 2012 Pearson Education, Inc.

13.  Eukaryotic cells –are more complex and larger than prokaryotic cells, –have more genes, and –store most of their genes on multiple chromosomes within the nucleus. The large, complex chromosomes of eukaryotes duplicate with each cell division © 2012 Pearson Education, Inc.

14.  Eukaryotic chromosomes are composed of chromatin consisting of –one long DNA molecule and –proteins that help maintain the chromosome structure and control the activity of its genes.  To prepare for division, the chromatin becomes –highly compact and –visible with a microscope. The large, complex chromosomes of eukaryotes duplicate with each cell division © 2012 Pearson Education, Inc.

15. Figure 8.3A

16. Figure 8.3B Sister chromatids Chromosomes Centromere Chromosome duplication Sister chromatids Chromosome distribution to the daughter cells DNA molecules

17.  Before a eukaryotic cell begins to divide, it duplicates all of its chromosomes, resulting in –two copies called sister chromatids –joined together by centromere.  When a cell divides, the sister chromatids –separate from each other, now called chromosomes, and –sort into separate daughter cells. The large, complex chromosomes of eukaryotes duplicate with each cell division © 2012 Pearson Education, Inc.

18.  The cell cycle is an ordered sequence of events that extends –from the time a cell is first formed from a dividing parent cell –until its own division. The cell cycle multiplies cells © 2012 Pearson Education, Inc.

19.  The cell cycle consists of two stages, characterized as follows: 1.Interphase: duplication of cell contents –G 1 —growth, increase in cytoplasm –S—duplication of chromosomes –G 2 —growth, preparation for division 2.Mitotic phase: division –Mitosis—division of the nucleus –Cytokinesis—division of cytoplasm The cell cycle multiplies cells © 2012 Pearson Education, Inc.

20. Figure 8.4 G 1 (first gap) S (DNA synthesis) G 2 (second gap) M Cytokinesis Mitosis I N T E R P H A S E PH A SE T T MI O IC

21.  Mitosis progresses through a series of stages: –prophase, –prometaphase, –metaphase, –anaphase, and –telophase.  Cytokinesis often overlaps telophase. Cell division is a continuum of dynamic changes © 2012 Pearson Education, Inc.

22.  A mitotic spindle is –required to divide the chromosomes, –composed of microtubules, and –produced by centrosomes, structures in the cytoplasm that –organize microtubule arrangement and –contain a pair of centrioles in animal cells. Cell division is a continuum of dynamic changes © 2012 Pearson Education, Inc. Video: Sea Urchin (time lapse) Video: Animal Mitosis

23. Figure 8.5_1 INTERPHASE MITOSIS Prophase Prometaphase Centrosome Early mitotic spindle Chromatin Fragments of the nuclear envelope Kinetochore Centrosomes (with centriole pairs) Centrioles Nuclear envelope Plasma membrane Chromosome, consisting of two sister chromatids Centromere Spindle microtubules

24.  Interphase –The cytoplasmic contents double, –two centrosomes form, –chromosomes duplicate in the nucleus during the S phase, and –nucleoli, sites of ribosome assembly, are visible. Cell division is a continuum of dynamic changes © 2012 Pearson Education, Inc.

25. Figure 8.5_left INTERPHASE MITOSIS ProphasePrometaphase Centrosome Early mitotic spindle Chromatin Fragments of the nuclear envelope Kinetochore Centrosomes (with centriole pairs) Centrioles Nuclear envelope Plasma membrane Chromosome, consisting of two sister chromatids Centromere Spindle microtubules

26.  Prophase –In the cytoplasm microtubules begin to emerge from centrosomes, forming the spindle. –In the nucleus –chromosomes coil and become compact and –nucleoli disappear. Cell division is a continuum of dynamic changes © 2012 Pearson Education, Inc.

27.  Prometaphase –Spindle microtubules reach chromosomes, where they –attach at kinetochores on the centromeres of sister chromatids and –move chromosomes to the center of the cell through associated protein “motors.” –Other microtubules meet those from the opposite poles. –The nuclear envelope disappears. Cell division is a continuum of dynamic changes © 2012 Pearson Education, Inc.

28. Figure 8.5_5 MITOSIS Anaphase Metaphase Telophase and Cytokinesis Metaphase plate Cleavage furrow Nuclear envelope forming Daughter chromosomes Mitotic spindle

29. Figure 8.5_right MITOSIS Anaphase Metaphase Telophase and Cytokinesis Metaphase plate Cleavage furrow Nuclear envelope forming Daughter chromosomes Mitotic spindle

30.  Metaphase –The mitotic spindle is fully formed. –Chromosomes align at the cell equator. –Kinetochores of sister chromatids are facing the opposite poles of the spindle. Cell division is a continuum of dynamic changes © 2012 Pearson Education, Inc.

31.  Anaphase –Sister chromatids separate at the centromeres. –Daughter chromosomes are moved to opposite poles of the cell as –motor proteins move the chromosomes along the spindle microtubules and –kinetochore microtubules shorten. –The cell elongates due to lengthening of nonkinetochore microtubules. Cell division is a continuum of dynamic changes © 2012 Pearson Education, Inc.

32.  Telophase –The cell continues to elongate. –The nuclear envelope forms around chromosomes at each pole, establishing daughter nuclei. –Chromatin uncoils and nucleoli reappear. –The spindle disappears. Cell division is a continuum of dynamic changes © 2012 Pearson Education, Inc.

33.  During cytokinesis, the cytoplasm is divided into separate cells.  The process of cytokinesis differs in animal and plant cells. Cell division is a continuum of dynamic changes © 2012 Pearson Education, Inc.

34.  In animal cells, cytokinesis occurs as 1.a cleavage furrow forms from a contracting ring of microfilaments, interacting with myosin, and 2.the cleavage furrow deepens to separate the contents into two cells. Cytokinesis differs for plant and animal cells © 2012 Pearson Education, Inc.

35. Figure 8.6A Cytokinesis Cleavage furrow Contracting ring of microfilaments Daughter cells Cleavage furrow

36. Figure 8.6A_1 Cleavage furrow

37. Figure 8.6A_2 Cleavage furrow Contracting ring of microfilaments Daughter cells

38.  In plant cells, cytokinesis occurs as 1.a cell plate forms in the middle, from vesicles containing cell wall material, 2.the cell plate grows outward to reach the edges, dividing the contents into two cells, 3.each cell now possesses a plasma membrane and cell wall. Cytokinesis differs for plant and animal cells © 2012 Pearson Education, Inc. Animation: Cytokinesis

39. Figure 8.6B Cytokinesis Cell wall of the parent cell Daughter nucleus Cell wall Plasma membrane Vesicles containing cell wall material Cell plate forming New cell wall Cell plate Daughter cells

40. Figure 8.6B_1 Cell wall of the parent cell Daughter nucleus Cell plate forming

41. Figure 8.6B_2 Cell wall Plasma membrane Vesicles containing cell wall material New cell wall Cell plateDaughter cells

42.  When the cell cycle operates normally, mitosis produces genetically identical cells for –growth, –replacement of damaged and lost cells, and –asexual reproduction. Review: Mitosis provides for growth, cell replacement, and asexual reproduction © 2012 Pearson Education, Inc. Video: Hydra Budding

43. Figure 8.10A

44. Figure 8.10B Cell replacement (in bone marrow) Asexual reproduction (of a hydra)

45.  Cancer cells –start out as normal body cells, –undergo genetic mutations, –lose the ability to control the tempo of their own division, and –causing disease. Introduction © 2012 Pearson Education, Inc.

46. Figure 8.0_3